Stroke

September 28, 2011

Strokes are the third leading cause of death in the united States, following coronary heart disease and cancer. The Centers for Disease Control estimates that every 45 seconds, someone in the United States suffers a new or recurrent stroke; every 3.1 minutes, someone in the United States dies of a stroke. Overall, men are 1.6 times more likely than women to have a stroke. However, this statistic can be misleading. While men are more likely to have a stroke than women when they are younger, by age 55, the risk is equal among women and men. Furthermore, women are nearly twice as likely as men to die of a stroke, making strokes the second leading cause of death in women after coronary heart disease.

The two most important things to know about strokes are that many are preventable, and that prompt diagnosis and treatment can save lives. Everyone should learn about the risk factors and the warning signs of stroke.

DEFINITION AND CAUSES

A stroke, or cerebrovascular accident (CVA), is a type of injury to the brain that occurs in one of two ways. The most common type of stroke is a nonhemor-rhagic or ischemic stroke which occurs when a vessel that supplies blood to an area of the brain is blocked, leading to the death of brain cells that are normally supplied by the oxygen carried in the blood. A hemorrhagic stroke occurs when a damaged blood vessel bleeds directly into the brain, also leading to the death of brain cells in that area. The area of cell death that results in either type of stroke is called an infarct.

ischemic strokes are most often caused by atherosclerotic thrombosis or cerebral embolism, each account for one third of all strokes. Atherosclerotic thrombosis is the development of stenosis (narrowing) or complete blockage of a blood vessel by a lipid-containing plaque. Because this is a slow process, there may be warning signs such as transient stroke symptoms before an actual stroke occurs. Cerebral embolism occurs when a fragment of a blood clot (thrombus) or atherosclerotic plaque breaks off and then lodges in a smaller blood vessel thus blocking blood flow. People with strokes caused by emboli have often had no warning signs beforehand. Some rarer causes of ischemic strokes are infectious or connective tissue diseases or a sudden increase in blood’s tendency to form a clot caused by other medical conditions.

Hemorrhagic strokes may be caused by a ruptured aneurysm (a bulging or outpouching of an arterial wall, usually the result of an artery with developmental defects from birth) or a ruptured arteriovenous (AV) malformation (an abnormal connection between the arterial and venous systems, also the result of developmental defects). They can also be caused by a hypertensive crisis, in which someone’s blood pressure increases so severely that even normal blood vessels will rupture and bleed. In any of these cases, bleeding may occur either very gradually or happen abruptly without warning.

SYMPTOMS

The initial symptoms of stroke are varied such as: sudden numbness or weakness of the face, arm, or leg, particularly on one side of the body; sudden confusion, or trouble speaking or understanding; sudden trouble with walking, dizziness, or loss of balance or coordination; or a sudden, severe headache with no known cause. The variety of presenting symptoms reflects the many different specialized areas of the brain in which a stroke can occur. A small stroke that occurs in the motor cortex of the brain, for example, may produce only a physical symptom such as weakness in one leg. On the other hand, a stroke in the language centers of the brain can produce sudden problems with communication such as slurred or incomprehensible speech. It is not uncommon for people to ignore the initial warning signs of a stroke if it is mild, or for other people to mistake the initial signs of a stroke for alcohol intoxication.

Sometimes, a person develops symptoms of a stroke that last less than a day, often lasting just a few minutes or hours. When this happens, it is called a transient ischemic attack (TIA). Transient ischemic attack may be caused by a partly occluded blood vessel, a small embo-lus that resolves, or intermittent small amounts of blood leakage from an aneurysm. TIAs should always prompt a rapid medical evaluation because the data show that approximately one third of people who have TIAs will eventually have a stroke. One recent study showed that of people evaluated in a hospital for TIAs, there was an 11% incidence of stroke just in the next 90 days.

TREATMENT AND PREVENTION

The treatment for acute strokes is still quite limited. If someone is having an ischemic stroke, and arrives at a hospital quickly enough, in some instances medication can be given that will break apart any clots that may be blocking the blood supply to that area of the brain. However, this type of medication is quite powerful and is not without its own risks. Also, if someone does not immediately come to the hospital when the first signs of a stroke arise, it is usually too late to give the medication. Once a stroke has occurred, treatment is generally limited to physical or speech therapy to improve functioning in the areas that have been affected by the stroke. Some people have complete or almost complete recoveries from strokes, while others are left with speech or motor problems that are permanent.

However, it is vital to remember that many strokes are preventable. The modifiable risk factors that are linked to having strokes include hypertension, cholesterol level of greater than 240 mg/dl, smoking, physical inactivity, obesity, carotid stenosis, alcohol consumption of more than five drinks per day, and atrial fibrillation. Smoking, for example, raises the chance of having a stroke to 1.5 times that of someone in the general population; hypertension raises the chance 3-5 times greater than normal. Not surprisingly, these risk factors are also generally associated with atherosclerosis, so that modifying these risk factors can also reduce the risk of having heart attacks and other health problems.

Of course, some risk factors are not themselves modifiable, such as being older or of non-Caucasian descent, having coronary heart disease or congestive heart failure, or a family history of stroke or TIAs. Also, there are physical disorders that increase the risk of having a stroke, such as sickle-cell anemia, certain bleeding disorders, or vasculitis caused by systemic lupus erythematosus, polyarteritis nodosa, or other conditions. However, the presence of these risk factors should lead individuals to pay even closer attention to prevention efforts aimed at the modifiable risk factors.

The evidence suggests that the most effective ways to reduce the chance of having a first stroke are good blood pressure control, using antithrombotic medicine (such as warfarin or aspirin) if an individual has a history of atrial fibrillation, and using aspirin or other antiplatelet therapy if an individual has had a myocardial infarction. Other things that are likely to help include lifestyle changes or the use of lipid-lowering medications to keep low-density lipoprotein (LDL) cholesterol below 130 mg/dl and smoking cessation. If an individual has already had a stroke, treatment of hypertension and hyperlipidemia, antithrombotic therapy (for atrial fibrillation), antiplatelet therapy (for myocardial infarction), and carotid endarterectomy (if an individual has carotid stenosis of 70% or greater and is not a high surgery risk) are all well-proven risk reduction methods.

Several risk factors for stroke are specific to women, including pregnancy, the use of oral contraceptives (OCs), or the use of hormone replacement therapy (HRT). A number of studies have shown an increased risk of strokes during pregnancy or childbirth, but this risk has been decreasing steadily over time. A 1996 study showed no increased risk for ischemic stroke during pregnancy itself, but did show a risk that was 8.7 times greater than normal during the first 6 weeks postpartum. The pregnancy-related causes of strokes are mainly preeclampsia or eclampsia (characterized by severe hypertension, protein in the urine, and edema developing during the pregnancy or within 48 hr postpartum); postpartum cerebral angiopathy (characterized by severe hypertension, headache, nausea and vomiting, and seizures or other neurologic signs developing minutes to weeks after delivery); and cerebral venous thrombosis (characterized by headaches and focal neurologic symptoms that develop during pregnancy or within a month of delivery). Immediate medical attention should be sought if these symptoms occur related to a pregnancy.

Oral contraceptive use and the risk of stroke are often overstated. While the early studies did show a link between OC use and strokes, most women now take newer OCs that have lower estrogen doses or contain desogestrel and most studies have shown these do not appear to elevate the risk of stroke, though not all studies agree. However, women who already have higher risk of strokes, such as those who smoke, have hyper-lipidemia or hypertension, or are over 35, should talk carefully with their doctors before initiating or continuing use of OCs. Also, since OCs are known to increase clotting factors in the blood, women with certain clotting disorders should not take OCs.

The use of HRT has been extensively scrutinized in recent years. Initially, HRT was hoped to be something that would decrease women’s risk of stroke or coronary heart disease, and certainly the early studies generally

seemed to support this belief, showing either a modest benefit or no difference in risk, with a couple of notable exceptions. However, in 2002, several researchers published a meta-analysis of previous research data on HRT. The data showed that HRT increased the risk of thromboembolic strokes, though not subarachnoid or intracerebral strokes, to 1.2 times that of other women. In addition, the risk of having any venous thromboem-bolism was shown to be increased by HRT to 2.1 times normal, and in the first year of use was 3.5 times normal. Another study published in 2002 showed no overall association of ischemic or hemorrhagic stroke with HRT, but did show a twofold increase in risk of those types of strokes during the first 6 months of hormone use. Because of the new data on HRT risks including stroke and breast cancer, HRT is no longer routinely recommended. However, in certain circumstances, the benefits of HRT may outweigh the potential risks, and some women will still choose to take hormones.

United States Department of Health and Human Services. (2003). A public action plan to prevent heart disease and stroke: Executive summary and overview. Atlanta, GA: Centers for Disease Control and Prevention.